Why won't my iPhone 6 let me open the email icon?

as soon as I tap the icon I get a blank screen it then closes back to the home screen. iv tried a reset, a turn of and on. iv closed all apps. cant think what else to do apart from a reset all setting etc?

Along with seaking of resets, Have you considered a backup through iTunes, Go into settings and open the General category, scroll down to reset - Go to the category of "Erase all contents bringing your device to factory in the box settings and set up all over again and before you use the restore from backup see what is under "Mail" and if anything delete it all, Restore and then set mail up all over manually. See if this does the tick.... Please keep in mind that I would do this ONLY if the first answer giveen fails to work.